Multi-scavenging functional separator ensuring the cycling stability of high energy density lithium-ion batteries

Abstract

Ni-rich LiNixCoyMn1-x-yO2 (NCM) materials are key cathode active materials for achieving high energy densities in lithium-ion batteries (LIBs). However, their practical applications are hindered by interfacial and structural instabilities such as microcracking, transition metal dissolution, and oxidative decomposition of the electrolyte at the cathode surface, which cause an increase in cell resistance and performance degradation. These problems are exacerbated by the parasitic reactions of impurities, such as H2O, HF, and transition metals during cycling. In this study, we fabricate a grafted polyacrylonitrile membrane containing zeolite (GPANZ) as a multi-scavenging functional separator to improve LIB cycling performance. GPANZ consists of H2O- and HF-removing functional zeolite and a transition-metal-chelate functional polyethyleneimine, thus effectively capturing various impurities in the cell. Therefore, the GPANZ separator can mitigate electrode and electrolyte degradation by suppressing the deleterious effects of impurities. The graphite/LiNi0.8Co0.1Mn0.1O2 cell with the GPANZ separator exhibits superior cycling performance in terms of discharge capacity, cycle life, and rate performance, especially at high temperatures. Our work highlights the necessity of removing impurities to ensure battery performance and provides new insights for designing functional separators for LIBs.